He was linked with Fiorentina last week.
Mulumbu said: "Every player has a price, if two clubs agree a fee there is nothing you can do.
"I have a contract with the club and I want to honour it but it is up to the club who has my registration.
"For me, I am still a West Brom player. Any club who wants me needs to convince them to sell me. I am ambitious and want to play at the top level all the time."